The vision of equal opportunity Dr. Martin Luther King Jr. set out during the 1963 March on Washington seems "even more elusive" now in light of the enduring racial wealth gap, President Barack Obama said here Wednesday.

"In too many communities across this country, in cities and suburbs and rural hamlets, the shadow of poverty casts a pall over our youth," the nation's first black president said at an event marking the 50th anniversary of King's "I have a dream" speech.

"For over a decade, working Americans of all races have seen their wages and incomes stagnate, even as corporate profits soar, even as the pay of a fortunate few explodes," Obama said.

"The position of all working Americans, regardless of color, has eroded, making the dream Dr. King described even more elusive," the president told a crowd at the Lincoln Memorial.

While progress has been made on civil rights, creating an economic system that "provides a fair shot for the many ... remains our great unfinished business," he said, acknowledging that the "task will not be easy."

"The March on Washington teaches us that we are not trapped by the mistakes of history, that we are masters of our fate. But it also teaches us that the promise of this nation will only be kept when we work together," Obama said.

"We'll have to reignite the embers of empathy and fellow feeling, the coalition of conscience that found expression in this place 50 years ago," he added.

The United States is indebted to the more than 200,000 people who gathered in Washington in 1963, Obama said.

"Because they marched, America became more free and more fair," the president said. EFE